Control of Carbon Content in Ultrafine Cemented Carbide by Heat Treatment in Reducing Atmospheres Containing Carbon Oxides

Abstract

In this work, the method of control of carbon content in the ultrafine-grained cemented carbide alloy was proposed. The treating of the WC-8Co-0.4VC-0.4Cr3C2 compacts was made in a CO + CO2 gas mixture at CO concentrations from 0 to 80 vol.% during 50 min at the initial stage of the conventional sintering at a temperature of 700 °C. Conditions for increasing and decreasing the carbon content are CO concentrations of CO in gas mix more than 65 vol.% and less than 35 vol.%, respectively. It is shown that even a small deviation from the stoichiometric carbon content (0.3 wt.%) leads to an increase in porosity and a multiple decrease in the strength of the ultrafine-grained cemented carbide. A comparative analysis with literature data showed that the obtained ultrafine-grained solid alloy WC-8Co-0.4VC-0.4Cr3C2 with stoichiometric composition is not inferior in hardness and toughness to the analogs obtained by hot pressing and electrospark sintering.